In the manufacture of tissue products, such as facial tissue, bath tissue, paper towels and the like, the tissue sheet is formed by depositing an aqueous suspension of papermaking fibers onto a forming fabric. The web is then transferred to a papermaking felt and dewatered as it passes through a pressure nip created between a pressure roll and a Yankee dryer as the wet web is transferred to the Yankee surface. Free water expressed from the web in the pressure nip is absorbed and carried away by the felt as the web transfers to the Yankee surface. The web is then final dried on the surface of the Yankee and subsequently creped to impart bulk and softness to the resulting tissue sheet. This method of making tissue sheets is commonly referred to as “wet-pressing” because of the method used to dewater the wet web.
The wet-pressing method has several distinct drawbacks. First, pressing the tissue web while wet densifies the web. Second, to restore a portion of the original web density it is necessary to crepe the web, which requires a large amount of energy to dry the web from a consistency of about 35 percent to a final dryness of about 95 percent. Third, because the web is densified by wet pressing immediately prior to drying, there is limited opportunity to impart structure to the web, which limits the tissuemaker's ability to modify the cross-machine direction properties of the web. As such, wet-pressed tissue products typically have only a modest degree of cross-machine direction stretch, relatively low cross-machine direction tensile energy absorption and modest degrees of durability and toughness in the cross-machine direction. These properties can be increased by increasing the cross-machine direction tensile strength, but in order to maximize product softness, the tensile strength must be limited to a reasonable level.
Therefore there is a need for a method of making wet-pressed tissue sheets having improved cross-machine direction properties, such as increased cross-machine direction stretch, increased cross-machine direction tensile energy absorption and increased degrees of durability and toughness in the cross-machine direction.